A man was struck by a Green Line train at the St. Paul Street station in Brookline Saturday night, according to the MBTA. The man, in his 20s, “came into contact” with the C Line train at about 10 p.m., MBTA spokesman Joshua Robin said in an e-mail. “He was conscious and alert” at the scene and was transported to Beth Israel Deaconess Medical Center, said Robin. A shuttle bus was set up between the St. Mary’s Street station and the Coolidge Corner station for two hours as transit police investigated the accident, he said.